/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/

/*
 *  Entropy accumulator implementation
 *
 *  Copyright (C) 2006-2016, ARM Limited, All Rights Reserved
 *  SPDX-License-Identifier: Apache-2.0
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
 *  not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *  This file is part of mbed TLS (https://tls.mbed.org)
 */

#include "tls/config.h"

#if defined(MBEDTLS_ENTROPY_C)

#if defined(MBEDTLS_TEST_NULL_ENTROPY)
#warning "**** WARNING!  MBEDTLS_TEST_NULL_ENTROPY defined! "
#warning "**** THIS BUILD HAS NO DEFINED ENTROPY SOURCES "
#warning "**** THIS BUILD IS *NOT* SUITABLE FOR PRODUCTION USE "
#endif

#include "tls/entropy.h"
#include "tls/entropy_poll.h"

#include <string.h>

#if defined(MBEDTLS_FS_IO)
#include <stdio.h>
#endif

#if defined(MBEDTLS_ENTROPY_NV_SEED)
#include "tls/platform.h"
#endif

#if defined(MBEDTLS_SELF_TEST)
#if defined(MBEDTLS_PLATFORM_C)
#include "tls/platform.h"
#else
#include <stdio.h>
#define mbedtls_printf     printf
#endif							/* MBEDTLS_PLATFORM_C */
#endif							/* MBEDTLS_SELF_TEST */

#if defined(MBEDTLS_HAVEGE_C)
#include "tls/havege.h"
#endif

/* Implementation that should never be optimized out by the compiler */
static void mbedtls_zeroize(void *v, size_t n)
{
	volatile unsigned char *p = v;
	while (n--) {
		*p++ = 0;
	}
}

#define ENTROPY_MAX_LOOP    256		/**< Maximum amount to loop before error */

void mbedtls_entropy_init(mbedtls_entropy_context *ctx)
{
	memset(ctx, 0, sizeof(mbedtls_entropy_context));

#if defined(MBEDTLS_THREADING_C)
	mbedtls_mutex_init(&ctx->mutex);
#endif

#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
	mbedtls_sha512_starts(&ctx->accumulator, 0);
#else
	mbedtls_sha256_starts(&ctx->accumulator, 0);
#endif
#if defined(MBEDTLS_HAVEGE_C)
	mbedtls_havege_init(&ctx->havege_data);
#endif

#if defined(MBEDTLS_TEST_NULL_ENTROPY)
	mbedtls_entropy_add_source(ctx, mbedtls_null_entropy_poll, NULL, 1, MBEDTLS_ENTROPY_SOURCE_STRONG);
#endif

#if !defined(MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES)
#if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)
	mbedtls_entropy_add_source(ctx, mbedtls_platform_entropy_poll, NULL, MBEDTLS_ENTROPY_MIN_PLATFORM, MBEDTLS_ENTROPY_SOURCE_STRONG);
#endif
#if defined(MBEDTLS_TIMING_C)
	mbedtls_entropy_add_source(ctx, mbedtls_hardclock_poll, NULL, MBEDTLS_ENTROPY_MIN_HARDCLOCK, MBEDTLS_ENTROPY_SOURCE_WEAK);
#endif
#if defined(MBEDTLS_HAVEGE_C)
	mbedtls_entropy_add_source(ctx, mbedtls_havege_poll, &ctx->havege_data, MBEDTLS_ENTROPY_MIN_HAVEGE, MBEDTLS_ENTROPY_SOURCE_STRONG);
#endif
#if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
	mbedtls_entropy_add_source(ctx, mbedtls_hardware_poll, NULL, MBEDTLS_ENTROPY_MIN_HARDWARE, MBEDTLS_ENTROPY_SOURCE_STRONG);
#endif
#if defined(MBEDTLS_ENTROPY_NV_SEED)
	mbedtls_entropy_add_source(ctx, mbedtls_nv_seed_poll, NULL, MBEDTLS_ENTROPY_BLOCK_SIZE, MBEDTLS_ENTROPY_SOURCE_STRONG);
#endif
#endif							/* MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES */
}

void mbedtls_entropy_free(mbedtls_entropy_context *ctx)
{
#if defined(MBEDTLS_HAVEGE_C)
	mbedtls_havege_free(&ctx->havege_data);
#endif
#if defined(MBEDTLS_THREADING_C)
	mbedtls_mutex_free(&ctx->mutex);
#endif
	mbedtls_zeroize(ctx, sizeof(mbedtls_entropy_context));
}

int mbedtls_entropy_add_source(mbedtls_entropy_context *ctx, mbedtls_entropy_f_source_ptr f_source, void *p_source, size_t threshold, int strong)
{
	int index, ret = 0;

#if defined(MBEDTLS_THREADING_C)
	if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0) {
		return (ret);
	}
#endif

	index = ctx->source_count;
	if (index >= MBEDTLS_ENTROPY_MAX_SOURCES) {
		ret = MBEDTLS_ERR_ENTROPY_MAX_SOURCES;
		goto exit;
	}

	ctx->source[index].f_source = f_source;
	ctx->source[index].p_source = p_source;
	ctx->source[index].threshold = threshold;
	ctx->source[index].strong = strong;

	ctx->source_count++;

exit:
#if defined(MBEDTLS_THREADING_C)
	if (mbedtls_mutex_unlock(&ctx->mutex) != 0) {
		return (MBEDTLS_ERR_THREADING_MUTEX_ERROR);
	}
#endif

	return (ret);
}

/*
 * Entropy accumulator update
 */
static int entropy_update(mbedtls_entropy_context *ctx, unsigned char source_id, const unsigned char *data, size_t len)
{
	unsigned char header[2];
	unsigned char tmp[MBEDTLS_ENTROPY_BLOCK_SIZE];
	size_t use_len = len;
	const unsigned char *p = data;

	if (use_len > MBEDTLS_ENTROPY_BLOCK_SIZE) {
#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
		mbedtls_sha512(data, len, tmp, 0);
#else
		mbedtls_sha256(data, len, tmp, 0);
#endif
		p = tmp;
		use_len = MBEDTLS_ENTROPY_BLOCK_SIZE;
	}

	header[0] = source_id;
	header[1] = use_len & 0xFF;

#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
	mbedtls_sha512_update(&ctx->accumulator, header, 2);
	mbedtls_sha512_update(&ctx->accumulator, p, use_len);
#else
	mbedtls_sha256_update(&ctx->accumulator, header, 2);
	mbedtls_sha256_update(&ctx->accumulator, p, use_len);
#endif

	return (0);
}

int mbedtls_entropy_update_manual(mbedtls_entropy_context *ctx, const unsigned char *data, size_t len)
{
	int ret;

#if defined(MBEDTLS_THREADING_C)
	if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0) {
		return (ret);
	}
#endif

	ret = entropy_update(ctx, MBEDTLS_ENTROPY_SOURCE_MANUAL, data, len);

#if defined(MBEDTLS_THREADING_C)
	if (mbedtls_mutex_unlock(&ctx->mutex) != 0) {
		return (MBEDTLS_ERR_THREADING_MUTEX_ERROR);
	}
#endif

	return (ret);
}

/*
 * Run through the different sources to add entropy to our accumulator
 */
static int entropy_gather_internal(mbedtls_entropy_context *ctx)
{
	int ret, i, have_one_strong = 0;
	unsigned char buf[MBEDTLS_ENTROPY_MAX_GATHER];
	size_t olen;

	if (ctx->source_count == 0) {
		return (MBEDTLS_ERR_ENTROPY_NO_SOURCES_DEFINED);
	}

	/*
	 * Run through our entropy sources
	 */
	for (i = 0; i < ctx->source_count; i++) {
		if (ctx->source[i].strong == MBEDTLS_ENTROPY_SOURCE_STRONG) {
			have_one_strong = 1;
		}

		olen = 0;
		if ((ret = ctx->source[i].f_source(ctx->source[i].p_source, buf, MBEDTLS_ENTROPY_MAX_GATHER, &olen)) != 0) {
			return (ret);
		}

		/*
		 * Add if we actually gathered something
		 */
		if (olen > 0) {
			entropy_update(ctx, (unsigned char)i, buf, olen);
			ctx->source[i].size += olen;
		}
	}

	if (have_one_strong == 0) {
		return (MBEDTLS_ERR_ENTROPY_NO_STRONG_SOURCE);
	}

	return (0);
}

/*
 * Thread-safe wrapper for entropy_gather_internal()
 */
int mbedtls_entropy_gather(mbedtls_entropy_context *ctx)
{
	int ret;

#if defined(MBEDTLS_THREADING_C)
	if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0) {
		return (ret);
	}
#endif

	ret = entropy_gather_internal(ctx);

#if defined(MBEDTLS_THREADING_C)
	if (mbedtls_mutex_unlock(&ctx->mutex) != 0) {
		return (MBEDTLS_ERR_THREADING_MUTEX_ERROR);
	}
#endif

	return (ret);
}

int mbedtls_entropy_func(void *data, unsigned char *output, size_t len)
{
	int ret, count = 0, i, done;
	mbedtls_entropy_context *ctx = (mbedtls_entropy_context *)data;
	unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];

	if (len > MBEDTLS_ENTROPY_BLOCK_SIZE) {
		return (MBEDTLS_ERR_ENTROPY_SOURCE_FAILED);
	}
#if defined(MBEDTLS_ENTROPY_NV_SEED)
	/* Update the NV entropy seed before generating any entropy for outside
	 * use.
	 */
	if (ctx->initial_entropy_run == 0) {
		ctx->initial_entropy_run = 1;
		if ((ret = mbedtls_entropy_update_nv_seed(ctx)) != 0) {
			return (ret);
		}
	}
#endif

#if defined(MBEDTLS_THREADING_C)
	if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0) {
		return (ret);
	}
#endif

	/*
	 * Always gather extra entropy before a call
	 */
	do {
		if (count++ > ENTROPY_MAX_LOOP) {
			ret = MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
			goto exit;
		}

		if ((ret = entropy_gather_internal(ctx)) != 0) {
			goto exit;
		}

		done = 1;
		for (i = 0; i < ctx->source_count; i++)
			if (ctx->source[i].size < ctx->source[i].threshold) {
				done = 0;
			}
	} while (!done);

	memset(buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE);

#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
	mbedtls_sha512_finish(&ctx->accumulator, buf);

	/*
	 * Reset accumulator and counters and recycle existing entropy
	 */
	memset(&ctx->accumulator, 0, sizeof(mbedtls_sha512_context));
	mbedtls_sha512_starts(&ctx->accumulator, 0);
	mbedtls_sha512_update(&ctx->accumulator, buf, MBEDTLS_ENTROPY_BLOCK_SIZE);

	/*
	 * Perform second SHA-512 on entropy
	 */
	mbedtls_sha512(buf, MBEDTLS_ENTROPY_BLOCK_SIZE, buf, 0);
#else							/* MBEDTLS_ENTROPY_SHA512_ACCUMULATOR */
	mbedtls_sha256_finish(&ctx->accumulator, buf);

	/*
	 * Reset accumulator and counters and recycle existing entropy
	 */
	memset(&ctx->accumulator, 0, sizeof(mbedtls_sha256_context));
	mbedtls_sha256_starts(&ctx->accumulator, 0);
	mbedtls_sha256_update(&ctx->accumulator, buf, MBEDTLS_ENTROPY_BLOCK_SIZE);

	/*
	 * Perform second SHA-256 on entropy
	 */
	mbedtls_sha256(buf, MBEDTLS_ENTROPY_BLOCK_SIZE, buf, 0);
#endif							/* MBEDTLS_ENTROPY_SHA512_ACCUMULATOR */

	for (i = 0; i < ctx->source_count; i++) {
		ctx->source[i].size = 0;
	}

	memcpy(output, buf, len);

	ret = 0;

exit:
#if defined(MBEDTLS_THREADING_C)
	if (mbedtls_mutex_unlock(&ctx->mutex) != 0) {
		return (MBEDTLS_ERR_THREADING_MUTEX_ERROR);
	}
#endif

	return (ret);
}

#if defined(MBEDTLS_ENTROPY_NV_SEED)
int mbedtls_entropy_update_nv_seed(mbedtls_entropy_context *ctx)
{
	int ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
	unsigned char buf[MBEDTLS_ENTROPY_MAX_SEED_SIZE];

	/* Read new seed  and write it to NV */
	if ((ret = mbedtls_entropy_func(ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE)) != 0) {
		return (ret);
	}

	if (mbedtls_nv_seed_write(buf, MBEDTLS_ENTROPY_BLOCK_SIZE) < 0) {
		return (MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR);
	}

	/* Manually update the remaining stream with a separator value to diverge */
	memset(buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE);
	mbedtls_entropy_update_manual(ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE);

	return (0);
}
#endif							/* MBEDTLS_ENTROPY_NV_SEED */

#if defined(MBEDTLS_FS_IO)
int mbedtls_entropy_write_seed_file(mbedtls_entropy_context *ctx, const char *path)
{
	int ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
	FILE *f;
	unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];

	if ((f = fopen(path, "wb")) == NULL) {
		return (MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR);
	}

	if ((ret = mbedtls_entropy_func(ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE)) != 0) {
		goto exit;
	}

	if (fwrite(buf, 1, MBEDTLS_ENTROPY_BLOCK_SIZE, f) != MBEDTLS_ENTROPY_BLOCK_SIZE) {
		ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
		goto exit;
	}

	ret = 0;

exit:
	fclose(f);
	return (ret);
}

int mbedtls_entropy_update_seed_file(mbedtls_entropy_context *ctx, const char *path)
{
	FILE *f;
	size_t n;
	unsigned char buf[MBEDTLS_ENTROPY_MAX_SEED_SIZE];

	if ((f = fopen(path, "rb")) == NULL) {
		return (MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR);
	}

	fseek(f, 0, SEEK_END);
	n = (size_t)ftell(f);
	fseek(f, 0, SEEK_SET);

	if (n > MBEDTLS_ENTROPY_MAX_SEED_SIZE) {
		n = MBEDTLS_ENTROPY_MAX_SEED_SIZE;
	}

	if (fread(buf, 1, n, f) != n) {
		fclose(f);
		return (MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR);
	}

	fclose(f);

	mbedtls_entropy_update_manual(ctx, buf, n);

	return (mbedtls_entropy_write_seed_file(ctx, path));
}
#endif							/* MBEDTLS_FS_IO */

#if defined(MBEDTLS_SELF_TEST)
#if !defined(MBEDTLS_TEST_NULL_ENTROPY)
/*
 * Dummy source function
 */
static int entropy_dummy_source(void *data, unsigned char *output, size_t len, size_t *olen)
{
	((void)data);

	memset(output, 0x2a, len);
	*olen = len;

	return (0);
}
#endif							/* !MBEDTLS_TEST_NULL_ENTROPY */

#if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)

static int mbedtls_entropy_source_self_test_gather(unsigned char *buf, size_t buf_len)
{
	int ret = 0;
	size_t entropy_len = 0;
	size_t olen = 0;
	size_t attempts = buf_len;

	while (attempts > 0 && entropy_len < buf_len) {
		if ((ret = mbedtls_hardware_poll(NULL, buf + entropy_len, buf_len - entropy_len, &olen)) != 0) {
			return (ret);
		}

		entropy_len += olen;
		attempts--;
	}

	if (entropy_len < buf_len) {
		ret = 1;
	}

	return (ret);
}

static int mbedtls_entropy_source_self_test_check_bits(const unsigned char *buf, size_t buf_len)
{
	unsigned char set = 0xFF;
	unsigned char unset = 0x00;
	size_t i;

	for (i = 0; i < buf_len; i++) {
		set &= buf[i];
		unset |= buf[i];
	}

	return (set == 0xFF || unset == 0x00);
}

/*
 * A test to ensure hat the entropy sources are functioning correctly
 * and there is no obvious failure. The test performs the following checks:
 *  - The entropy source is not providing only 0s (all bits unset) or 1s (all
 *    bits set).
 *  - The entropy source is not providing values in a pattern. Because the
 *    hardware could be providing data in an arbitrary length, this check polls
 *    the hardware entropy source twice and compares the result to ensure they
 *    are not equal.
 *  - The error code returned by the entropy source is not an error.
 */
int mbedtls_entropy_source_self_test(int verbose)
{
	int ret = 0;
	unsigned char buf0[2 * sizeof(unsigned long long int)];
	unsigned char buf1[2 * sizeof(unsigned long long int)];

	if (verbose != 0) {
		mbedtls_printf("  ENTROPY_BIAS test: ");
	}

	memset(buf0, 0x00, sizeof(buf0));
	memset(buf1, 0x00, sizeof(buf1));

	if ((ret = mbedtls_entropy_source_self_test_gather(buf0, sizeof(buf0))) != 0) {
		goto cleanup;
	}
	if ((ret = mbedtls_entropy_source_self_test_gather(buf1, sizeof(buf1))) != 0) {
		goto cleanup;
	}

	/* Make sure that the returned values are not all 0 or 1 */
	if ((ret = mbedtls_entropy_source_self_test_check_bits(buf0, sizeof(buf0))) != 0) {
		goto cleanup;
	}
	if ((ret = mbedtls_entropy_source_self_test_check_bits(buf1, sizeof(buf1))) != 0) {
		goto cleanup;
	}

	/* Make sure that the entropy source is not returning values in a
	 * pattern */
	ret = memcmp(buf0, buf1, sizeof(buf0)) == 0;

cleanup:
	if (verbose != 0) {
		if (ret != 0) {
			mbedtls_printf("failed\n");
		} else {
			mbedtls_printf("passed\n");
		}

		mbedtls_printf("\n");
	}

	return (ret != 0);
}

#endif							/* MBEDTLS_ENTROPY_HARDWARE_ALT */

/*
 * The actual entropy quality is hard to test, but we can at least
 * test that the functions don't cause errors and write the correct
 * amount of data to buffers.
 */
int mbedtls_entropy_self_test(int verbose)
{
	int ret = 1;
#if !defined(MBEDTLS_TEST_NULL_ENTROPY)
	mbedtls_entropy_context ctx;
	unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE] = { 0 };
	unsigned char acc[MBEDTLS_ENTROPY_BLOCK_SIZE] = { 0 };
	size_t i, j;
#endif							/* !MBEDTLS_TEST_NULL_ENTROPY */

	if (verbose != 0) {
		mbedtls_printf("  ENTROPY test: ");
	}
#if !defined(MBEDTLS_TEST_NULL_ENTROPY)
	mbedtls_entropy_init(&ctx);

	/* First do a gather to make sure we have default sources */
	if ((ret = mbedtls_entropy_gather(&ctx)) != 0) {
		goto cleanup;
	}

	ret = mbedtls_entropy_add_source(&ctx, entropy_dummy_source, NULL, 16, MBEDTLS_ENTROPY_SOURCE_WEAK);
	if (ret != 0) {
		goto cleanup;
	}

	if ((ret = mbedtls_entropy_update_manual(&ctx, buf, sizeof buf)) != 0) {
		goto cleanup;
	}

	/*
	 * To test that mbedtls_entropy_func writes correct number of bytes:
	 * - use the whole buffer and rely on ASan to detect overruns
	 * - collect entropy 8 times and OR the result in an accumulator:
	 *   any byte should then be 0 with probably 2^(-64), so requiring
	 *   each of the 32 or 64 bytes to be non-zero has a false failure rate
	 *   of at most 2^(-58) which is acceptable.
	 */
	for (i = 0; i < 8; i++) {
		if ((ret = mbedtls_entropy_func(&ctx, buf, sizeof(buf))) != 0) {
			goto cleanup;
		}

		for (j = 0; j < sizeof(buf); j++) {
			acc[j] |= buf[j];
		}
	}

	for (j = 0; j < sizeof(buf); j++) {
		if (acc[j] == 0) {
			ret = 1;
			goto cleanup;
		}
	}

#if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
	if ((ret = mbedtls_entropy_source_self_test(0)) != 0) {
		goto cleanup;
	}
#endif

cleanup:
	mbedtls_entropy_free(&ctx);
#endif							/* !MBEDTLS_TEST_NULL_ENTROPY */

	if (verbose != 0) {
		if (ret != 0) {
			mbedtls_printf("failed\n");
		} else {
			mbedtls_printf("passed\n");
		}

		mbedtls_printf("\n");
	}

	return (ret != 0);
}
#endif							/* MBEDTLS_SELF_TEST */

#endif							/* MBEDTLS_ENTROPY_C */
